By Rosie Hodnett (University of Leicester)
Omega bands are wave-like structures in the aurora which drift eastward in the auroral dawn sector. Omega bands carry pairs of upward and downward field aligned current (FAC). This moving current structure causes ground-based magnetic perturbations, which can be observed in magnetometer data, especially in the Y/eastward component (b). The perturbations can be large, resulting in large spikes of dB/dt (c). Spikes in dB/dt can cause geomagnetically induced currents (GICs) in ground-based infrastructure such as in the power grid, and so can be damaging.
In this paper, we investigate three omega band events which have different values of dB/dt. Using ground-based magnetometer data, we show that the events with larger spikes in dB/dt occur when the eastward speed of the omega bands is faster. This occurs when there is strong driving of the magnetosphere, for example during a geomagnetic storm, which leads to greater ionospheric convection speeds and hence greater omega band speeds. Additionally, EISCAT (European Incoherent SCATter radar) data shows large enhancements of electron density at low altitudes (a).
We also find that omega bands are associated with both electron (f) and proton (e) emissions, suggesting that they have a complicated current structure. Additionally, we show that omega bands are visible in the region 1 region 2 FAC boundary in AMPERE (Active Magnetosphere and Planetary Electrodynamics Response Experiment) data (d).
See publication for more details:
Hodnett, R. M., Milan, S. E., Vines, S. K., Gjerloev, J. W., & Paxton, L. J. (2026). A Multi-event comparison of dB/dt resulting from omega band aurora. Journal of Geophysical Research: Space Physics, 131, e2026JA035740. https://doi.org/10.1029/2026JA035740

(a) EISCAT very high frequency electron density measurements of omega band aurora on 2012-09-05. (b-c) Tromsø magnetometer data and dB/dt for 2012-09-05. (d) Keogram of AMPERE region 1/ region 2 FACs at 06 MLT (dawn sector) on 2012-07-15. (e-f) DMSP SSUSI data showing omega band aurora on 2012-07-14.